Secondary battery

ABSTRACT

A secondary battery includes an electrode assembly, a case accommodating the electrode assembly, and a cap assembly coupled to the case to seal the case, and the case includes a bottom portion, long side portions bent and extended from the bottom portion, a first short side portion bent and extended from the bottom portion, and second short side portions bent and extended from the long side portions, the first short side portion and the second short side portions connected to each other to define a short side portion, and curvatures located between the first short side portion and the second short side portions.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2019-0080772, filed on Jul. 4, 2019 in the KoreanIntellectual Property Office, the entire content of which is hereinincorporated by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to a secondarybattery.

2. Description of the Related Art

A battery may be classified as a prismatic type, a cylindrical type, apouch type, etc., according to the shape of a case. A prismatic orcylindrical battery may be manufactured by inserting an electrodeassembly having a positive electrode, a negative electrode, and aseparator into a metal can and sealing the electrode assembly, while apouch type battery may be manufactured by enclosing an electrodeassembly using an aluminum foil coated with an insulator.

Traditional battery can manufacturing methods may include a deep drawingprocess, an impact process, and so on. In an example, the deep drawingprocess is performed such that a sheet-shaped metal plate is placed on amolding die and punching operations are performed on the metal plateabout ten times using a punch, thereby completing the can. In anotherexample, the impact process is performed such that a slug in the form ofa billet is placed on a molding die and a strong punching operation isperformed on the slug about one time using a punch, thereby completingthe can. The impact process can reduce the number of processing steps,thereby lowering the manufacturing cost.

However, the conventional deep drawing process and the conventionalimpact process are both limited in reducing a can thickness due to therespective manufacturing process characteristics and have a largedeviation in the thickness of the can according to the area of the can.In addition, the conventional deep drawing process and the conventionalimpact process are problematic in that the manufacturing cost of thebattery can is quite high.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the describedtechnology and, therefore, it may contain information that does not formthe prior art that is already known in this country to a person ofordinary skill in the art.

SUMMARY

According to an aspect of embodiments of the present invention, asecondary battery has a bending type can, or case, which may have nothickness deviation in various areas of the can by reducing thethickness of the can and increasing dimensional accuracy, and which hasimproved safety by providing curved portions at corners where three orfour sides meet.

According to another aspect of embodiments of the present invention, asecondary battery has a bending type can, which includes desirablyshaped curved portions by providing curvatures at corners where three orfour sides meet, the curvatures overlapping with each other when thecorners are bent, thereby preventing or substantially preventingpinholes from being generated during welding.

According to one or more embodiments of the present invention, asecondary battery includes: an electrode assembly; a case accommodatingthe electrode assembly, and a cap assembly coupled to the case to sealthe case, wherein the case includes a bottom portion, long side portionsbent and extended from the bottom portion, a first short side portionbent and extended from the bottom portion, and second short sideportions bent and extended from the long side portions, the first shortside portion and the second short side portions connected to each otherto define a short side portion, and curvatures located between the firstshort side portion and the second short side portions.

The curvatures may be located at regions where the first short sideportion and the second short side portions meet.

The curvatures may include a first curvature located in the first shortside portion, and a second curvature located in each of the second shortside portions.

The first curvature and the second curvature may overlap with eachother.

The first curvature and the second curvature may be in an asymmetricconfiguration.

The first curvature may be larger than the second curvature.

The second curvature may be larger than the first curvature.

The first curvature may have a larger curvature radius than the secondcurvature.

The second curvature may have a larger curvature radius than the firstcurvature.

The secondary battery may further include curved portions located atregions where the bottom portion, the long side portions, and the shortside portion including the first short side portion having the firstcurvature, and the second short side portion having the secondcurvature, meet.

The short side portion may further include welding portions, and thewelding portions may include a first welding portion located betweeneach of the curved portions and each of the first short side portion andthe second short side portions, and a second welding portion locatedbetween the second short side portions.

The curvatures may be located at centers of regions where the firstshort side portion and the second short side portions meet.

The curvatures may be connected longer to the first short side portionthan to the second short side portions, or the curvatures may beconnected longer to the second short side portions than to the firstshort side portion.

The first short side portion may extend from both end portions of thebottom portion, the second short side portions may extend from both endsof the long side portions, and the short side portion may be defined onboth sides of the bottom portion and the long side portions.

As described above, according to one or more embodiments of the presentinvention, a secondary battery having a bending type can is provided,which may have no thickness deviation in various areas of the can byreducing the thickness of the can and increasing dimensional accuracy,and which may improve safety by providing curved portions at cornerswhere three or four sides meet. In some examples, asymmetricalcurvatures are provided at vertexes (corners) where the first short sideportion bent from the bottom portion and the second short portions bentfrom the long side portions meet, such that the asymmetrical curvaturesoverlap with each other when they are bent, thereby providing desirablyshaped, symmetrical curved portions at the corners where the bottomportion, the long side portions, the first short side portion, and thesecond short side portions meet.

In addition, according to one or more embodiments of the presentinvention, a secondary battery having a bending type can is provided,which includes desirably shaped curved portions by providing curvaturesat corners where three or four sides meet, the curvatures overlappingwith each other when the corners are bent, thereby preventing orsubstantially preventing pinholes from being generated during welding.In some examples, according to the present invention, desirably shaped,symmetrical curved portions are provided by the asymmetrical curvaturesoverlapping with each other, and boundary regions between the first andsecond short side portions are spaced by a distance (e.g., apredetermined distance) apart from the curved portions, thereby easilyperforming welding without pinholes generated at the curved portions andthe boundary regions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example secondary batteryaccording to an embodiment of the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating example secondarybatteries according to embodiments of the present invention.

FIGS. 3A and 3B are perspective views illustrating an example method formanufacturing an example secondary battery according to an embodiment ofthe present invention.

FIGS. 4A to 4D are partially enlarged plan views illustrating an examplemethod for manufacturing an example secondary battery according to anembodiment of the present invention.

FIGS. 5A and 5B are partially enlarged plan views illustrating anexample method for manufacturing an example secondary battery.

FIGS. 6A to 6C are perspective views illustrating an example method formanufacturing an example secondary battery according to an embodiment ofthe present invention.

FIGS. 7A and 7B are partially enlarged plan views illustrating a methodfor manufacturing a secondary battery according to an exampleembodiment.

DESCRIPTION OF REFERENCE NUMERALS

100, 200: Secondary battery 110: Electrode assembly 120: First terminal130: Second terminal 140: Can 140A: Metal plate 141: Bottom portion 142,143: Long side portion 144, 145: Short side portion 146: Welding portion147: Opening 1440A, 1440B: Curvature 1441: First curvature 1442: Secondcurvature 1550A, 1550B: Curved portion

DETAILED DESCRIPTION

Herein, some example embodiments of the present invention will bedescribed in further detail.

Various embodiments of the present invention may be embodied in manydifferent forms and should not be construed as being limited to theexample embodiments set forth herein. Rather, these example embodimentsof the disclosure are provided so that this disclosure will be thoroughand complete and will convey inventive concepts of the disclosure tothose skilled in the art.

In addition, in the accompanying drawings, sizes or thicknesses ofvarious components may be exaggerated for brevity and clarity. Likenumbers refer to like elements throughout. In addition, it is to beunderstood that when an element A is referred to as being “connected to”an element B, the element A may be directly connected to the element Bor one or more intervening elements C may be present and the element Aand the element B may be indirectly connected to each other.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the disclosure. Asused herein, the singular forms are intended to include the plural formsas well, unless the context clearly indicates otherwise. It is to befurther understood that the terms “comprise or include” and/or“comprising or including,” when used in this specification, specify thepresence of stated features, numbers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, numbers, steps, operations, elements,components, and/or groups thereof.

It is to be understood that, although the terms “first,” “second,” etc.may be used herein to describe various members, elements, regions,layers, and/or sections, these members, elements, regions, layers,and/or sections should not be limited by these terms. These terms areused to distinguish one member, element, region, layer, and/or sectionfrom another. Thus, for example, a first member, a first element, afirst region, a first layer, and/or a first section discussed belowcould be termed a second member, a second element, a second region, asecond layer, and/or a second section without departing from theteachings of the present disclosure.

Spatially relative terms, such as “below,” “beneath,” “lower,” “above,”“upper,” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It is to be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “on” or “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below.

The term “welding portion” used throughout this specification can bereferred to as a temporary welding portion and/or a welding portion insome cases, which is for representing the welding sequence and functionbut is not intended to limit the invention. In addition, the term“welding” as used herein mainly means laser welding, and examples of alaser used for welding may include, but are not limited to, CO2 laser,fiber laser, disk laser, semiconductor laser, and/or yttrium aluminumgarnet (YAG) laser. In addition, the terms “second short side portion”and “third short side portion” can be referred to as second short sideportions, in some cases.

Unless otherwise defined, all terms used herein (including technical orscientific terms) have the same meanings as those generally understoodby those skilled in the art to which the inventive concept pertains.Such terms as those defined in a generally used dictionary are to beinterpreted as having meanings equal to the contextual meanings in therelevant field of art, and are not to be interpreted as having idealizedor excessively formal meanings unless clearly defined herein.

FIG. 1 is a perspective view illustrating an example secondary batteryaccording to an embodiment of the present invention. In the exampleshown in FIG. 1, a secondary battery 100 may include an electrodeassembly 110 (110 and 210 in the examples shown in FIGS. 2A and 2B), afirst terminal 120, a second terminal 130, a can, or case, 140, and acap assembly 150.

In some examples, the can 140 may be provided by blanking and/ornotching, bending, and welding a metal plate and may have asubstantially hexahedral shape having an opening through which theelectrode assembly 110 is inserted and placed and the cap assembly 150is mounted. In some examples, the can 140 may include a rectangularbottom portion 141 having long sides and short sides, long side portions142 and 143 bent and extended from the respective long sides of thebottom portion 141 to the cap assembly 150, and short side portions 144and 145 extended from the respective short sides of the bottom portion141 and the long side portions 142 and 143.

In FIG. 1, the can 140 and the cap assembly 150 assembled to each otherare illustrated, such that the opening, which is a substantially openedpart of a region corresponding to the cap assembly 150, is notillustrated in FIG. 1. In an embodiment, the interior surface and/or theexterior surface of the can 140 may be subjected to insulation treatmentsuch that the can 140 is insulated from the electrode assembly, thefirst terminal 120, the second terminal 130, and the cap assembly 150.

FIGS. 2A and 2B are cross-sectional views illustrating example secondarybatteries 100 and 200. In the example shown in FIG. 2A, the secondarybattery 100 may include an electrode assembly 110 having a winding axisextending in a horizontal direction (i.e., in a direction substantiallyparallel with a lengthwise direction of the cap assembly 150). In theexample shown in FIG. 2B, the secondary battery 200 may include anelectrode assembly 210 having a winding axis extending in a verticaldirection (i.e., in a direction substantially perpendicular to thelengthwise direction of the cap assembly 150). In some examples, theelectrode assembly may be a stacked electrode assembly, rather than awound electrode assembly.

The secondary battery 100 shown in FIG. 2A will now be described. Theelectrode assembly 110 may be formed by winding or stacking a stackedstructure including a first electrode plate 111, a separator 113, and asecond electrode plate 112, which are thin plates or layers. In someexamples, the first electrode plate 111 may operate as a negativeelectrode and the second electrode plate 112 may operate as a positiveelectrode, or vice versa. In some examples, the first electrode plate111 may be formed by coating a first active material, such as graphiteor carbon, on a first electrode collector made of a metal foil, such ascopper, a copper alloy, nickel, or a nickel alloy, and may include afirst uncoated portion 111 a that is not coated with the first activematerial. In some examples, the second electrode plate 112 may be formedby coating a second active material, such as a transition metal oxide,on a second electrode collector made of a metal foil, such as aluminumor an aluminum alloy, and may include a second uncoated portion 112 athat is not coated with the second electrode material. In some examples,the separator 113, which is located between the first and secondelectrode plates 111 and 112, may prevent or substantially prevent shortcircuits between the first and second electrode plates 111 and 112, andmay allow lithium ions to move. In an embodiment, the separator 113 mayinclude polyethylene, polypropylene, or a composite film of polyethyleneand polypropylene. In an embodiment, the separator 113 may be replacedby an inorganic solid electrolyte, such as a sulfide-based compound, anoxide-based compound, or a sulphate compound, not necessitating aliquid- or gel-phase electrolyte solution. The first terminal 120 andthe second terminal 130 electrically connected to the first electrodeplate 111 and the second electrode plate 112, respectively, are locatedat opposite ends of the electrode assembly 110. In some examples, theelectrode assembly 110 may be accommodated in the can 140 with anelectrolytic solution. In some examples, the electrolytic solution mayinclude an organic solvent, such as ethylene carbonate (EC), propylenecarbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC),or dimethyl carbonate (DMC), and a lithium salt, such as LiPF₆ or LiBF₄.In some examples, if the inorganic solid electrolyte is used, theelectrolytic solution may be omitted.

The first terminal 120 may be made of a metal and may be electricallyconnected to the first electrode plate 111. In some examples, the firstterminal 120 may include a first collector plate 121, a first terminalpillar 122, and a first terminal plate 124. In some examples, the firstcollector plate 121 may be brought into contact with the first uncoatedportion 111 a protruding at an end of the electrode assembly 110. In anembodiment, the first collector plate 121 may be welded to the firstuncoated portion 111 a. In some examples, the first collector plate 121may be substantially in an inverted L-shaped (“┌”) configuration and mayhave a terminal hole 121 a located in a top portion thereof. In someexamples, the first terminal pillar 122 may be inserted into theterminal hole 121 a, followed by riveting and/or welding. In someexamples, the first collector plate 121 may be made of copper or acopper alloy. In some examples, the first terminal pillar 122 penetratesthe cap plate 151 to be described later and is electrically connected tothe first collector plate 121 under the cap plate 151. In addition, insome examples, while the first terminal pillar 122 is upwardly protrudedand extended to an upper portion of the cap plate 151 by a length (e.g.,a predetermined length), a flange 122 a may be located below the capplate 151 to prevent or substantially prevent the first terminal pillar122 from being dislodged from the cap plate 151. In an embodiment, aportion of the first terminal pillar 122 positioned below the flange 122a is fitted into the first terminal hole 121 a of the first collectorplate 121, followed by riveting and/or welding. In some examples, thefirst terminal pillar 122 may be electrically insulated from the capplate 151. In some examples, boundary regions of the upwardly exposedfirst terminal pillar 122 and the first terminal plate 124 may be weldedto each other. For example, a laser beam may be supplied to the boundaryregions of the upwardly exposed first terminal pillar 122 and the firstterminal plate 124 to melt the boundary regions, followed by cooling,thereby welding the boundary regions. The welded regions are designatedby reference numeral 125 in FIG. 2A. In an embodiment, a bus bar made ofaluminum or an aluminum alloy may be welded to the first terminal plate124.

The second terminal 130 may also be made of a metal and may beelectrically connected to the second electrode plate 112. In someexamples, the second terminal 130 may include a second collector plate131, a second terminal pillar 132, and a second terminal plate 134. Insome examples, the second collector plate 131 may be brought intocontact with the second uncoated portion 112 a protruding at an end ofthe electrode assembly 110. In some examples, the second collector plate131 may be substantially in an inverted L-shaped (“┐”) configuration andmay have a terminal hole 131 a located in a top portion thereof. In someexamples, the second terminal pillar 132 may be inserted into theterminal hole 131 a and then coupled thereto. In some examples, thefirst collector plate 121 may be made of, for example, but is notlimited to, aluminum or an aluminum alloy. In some examples, the secondterminal pillar 132 penetrates the cap plate 151 to be described laterand is electrically connected to the second collector plate 131 underthe cap plate 151. In addition, in some examples, while the secondterminal pillar 132 is upwardly protruded and extended to an upperportion of the cap plate 151 by a length (e.g., a predetermined length),a flange 132 a may be located below the cap plate 151 to prevent orsubstantially prevent the second terminal pillar 132 from beingdislodged from the cap plate 151. In an embodiment, a portion of thesecond terminal pillar 132 positioned below the flange 132 a is fittedinto the second terminal hole 131 a of the second collector plate 131,followed by riveting and/or welding. In an embodiment, the secondterminal pillar 132 may be electrically insulated from the cap plate151. In some examples, the second terminal pillar 132 may be made ofaluminum or an aluminum alloy. In an embodiment, the second terminalplate 134 has a hole 134 a. In addition, the second terminal plate 134is coupled to the second terminal pillar 132. That is, the secondterminal pillar 132 is coupled to the hole 134 a of the second terminalplate 134. In an embodiment, the second terminal pillar 132 and thesecond terminal plate 134 may be riveted and/or welded to each other. Insome examples, boundary regions of the upwardly exposed second terminalpillar 132 and the second terminal plate 134 may be welded to eachother. For example, a laser beam may be supplied to the boundary regionsof the upwardly exposed second terminal pillar 132 and the secondterminal plate 134 to melt the boundary regions, followed by cooling,thereby welding the boundary regions. The welded regions are designatedby reference numeral 135 in FIG. 2A. In an embodiment, a bus bar made ofaluminum or an aluminum alloy may be easily welded to the secondterminal plate 134. In an embodiment, the second terminal plate 134 maybe electrically connected to the cap plate 151. Thus, the cap plate 151and the can 140, which will be described below, may have the samepolarity as the second terminal 130 (e.g., a positive polarity).

The cap assembly 150 may be coupled to the can 140. In some examples,the cap assembly 150 may include the cap plate 151, a seal gasket 152, aplug 153, a safety vent 154, an upper coupling member 155, and a lowerinsulating member 156. The cap plate 151 may seal the opening of thecase 140, and may be made of a same material as the case 140. In someexamples, the cap plate 151 may be coupled to the can 140 by laserwelding. As described above, in an embodiment, since the cap plate 151has the same polarity as the second terminal 130, the cap plate 151 andthe can 140 may have the same polarity. The seal gasket 152 made of aninsulating material may be located between each of the first terminalpillar 122 and the second terminal pillar 132 and the cap plate 151 at abottom end of the cap plate 151 and may seal regions between each of thefirst terminal pillar 122 and the second terminal pillar 132 and the capplate 151. The seal gasket 152 may prevent or substantially preventexternal moisture from permeating into the secondary battery 100 andprevent or substantially prevent the electrolyte accommodated in thesecondary battery 100 from being effused outside. The plug 153 may sealan electrolyte injection hole 151 a of the cap plate 151. The safetyvent 154 may be installed in a vent hole 151 b of the cap plate 151 andmay have a notch configured to be openable at a preset pressure. Theupper coupling member 155 may be located between each of the firstterminal pillar 122 and the second terminal pillar 132 and the cap plate151 at a top end of the cap plate 151. In addition, the upper couplingmember 155 may closely contact the cap plate 151. In addition, the uppercoupling member 155 may also closely contact and the seal gasket 152. Inan embodiment, the upper coupling member 155 may insulate the firstterminal pillar 122 and the second terminal pillar 132 from the capplate 151. In some examples, the upper coupling member 155 located inthe second terminal pillar 132 may electrically connect the secondterminal plate 134 and the cap plate 151 to each other. Accordingly, thesecond terminal 130 may have the same polarity as the cap plate 151 andthe can 140. The lower insulating member 156 may be located between eachof the first collector plate 121 and the second collector plate 131 andthe cap plate 151 and may prevent or substantially prevent anunnecessary short circuit from being generated. That is, the lowerinsulating member 156 may prevent or substantially prevent shortcircuits from being generated between the first collector plate 121 andthe cap plate 151 and between the second collector plate 131 and the capplate 151.

The secondary battery 200 shown in FIG. 2B will now be described. Thesecondary battery 200 is different from the secondary battery 100 interms of the construction of the electrode assembly 210 and theconnection relationships between the electrode assembly 210 and each ofthe terminals 120 and 130. A first electrode tab 211 a may be positionedbetween the electrode assembly 210 and a first terminal pillar 122 of afirst terminal 120, and a second electrode tab 212 a may be positionedbetween the electrode assembly 210 and a second terminal pillar 132 of asecond terminal 130. In an embodiment, the first electrode tab 211 a maybe extended from a top end of the electrode assembly 210 to a bottom endof the first terminal pillar 122 of the first terminal 120 to beelectrically connected or welded to a planar flange 122 a provided inthe first terminal pillar 122. In addition, the second electrode tab 212a may be extended from a top end of the electrode assembly 210 to abottom end of the second terminal pillar 132 of the second terminal 130to be electrically connected or welded to a planar flange 132 a providedin the second terminal pillar 132. The first electrode tab 211 a may beeither a first uncoated portion of the first electrode plate 211 of theelectrode assembly 210, which is not coated with a first active material211 b, or a separate member connected to the first uncoated portion.Here, the first uncoated portion may be made of a same material as thefirst electrode plate 211, and the separate member may be one selectedfrom the group consisting of nickel, a nickel alloy, copper, a copperalloy, aluminum, an aluminum alloy, and equivalents thereof. Inaddition, the second electrode tab 212 a may be either a second uncoatedportion of the second electrode plate 212 of the electrode assembly 210,which is not coated with a second active material, or a separate memberconnected to the second uncoated portion. Here, the second uncoatedportion may be made of a same material as the second electrode plate212, and the separate member may be one selected from the groupconsisting of aluminum, an aluminum alloy, nickel, a nickel alloy,copper, a copper alloy, and equivalents thereof.

As described above, in an embodiment, since a winding axis of theelectrode assembly and terminal axes of the terminals are parallel orhorizontal with each other, the electrode assembly has excellentelectrolyte impregnation capability when an electrolyte is injected, andinternal gases may be rapidly transferred to a safety vent duringovercharging to facilitate the safety vent 154 quickly operating. In anembodiment, electrode tabs (uncoated portions or separate members) ofthe electrode assembly are directly electrically connected to theterminals, which shortens electrical paths, thereby reducing internalresistance of the secondary battery 200 while reducing the number ofcomponents of the secondary battery 200.

The can 140 manufactured by an example method, which will be describedbelow, may be employed to the secondary batteries 100 and 200 shown inFIGS. 1, 2A, and 2B.

FIGS. 3A and 3B are perspective views illustrating an example method formanufacturing example secondary battery 100, 200. FIG. 3A shows a can140 at an initial stage of manufacture.

In the example shown in FIG. 3A, a substantially planar metal plate 140Ahaving a uniform thickness may be provided. In some examples, the metalplate 140A may include any of aluminum (Al), iron (Fe), copper (Cu),titanium (Ti), nickel (Ni), magnesium (Mg), chromium (Cr), manganese(Mn), zinc (Zn), or alloys of these elements. In some examples, themetal plate 140A may include nickel (Ni) plated iron (Fe) or SUS (e.g.,SUS 301, SUS 304, SUS 305, SUS 316L, or SUS 321).

In some examples, the metal plate 140A may have a thickness in a rangefrom approximately 0.1 mm to approximately 10 mm, and a deviation in thethickness of the metal plate 140A in all areas may be in a range fromapproximately 0.1% to approximately 1%. Therefore, the present inventionmay provide the can 140 that is relatively thin and has a smallthickness deviation, compared to a conventional can.

In some examples, the metal plate 140A may be preprocessed to facilitatea bending process, a notching process, and/or a welding process, whichwill be described below. In some examples, the metal plate 140A may besubjected to annealing treatment performed in a gas atmosphere (e.g., apredetermined gas atmosphere) and a temperature range (e.g., apredetermined temperature range) for a period of time (e.g., apredetermined period of time). In some examples, the annealing treatmentmay be performed in an atmosphere of inert gas, such as argon (Ar) ornitrogen (N₂) at a temperature in a range from approximately 300° C. toapproximately 1000° C. for approximately 10 seconds to approximately 60minutes. The annealing treatment may increase the elastic modulus of themetal plate 140A by approximately 5% to approximately 60%. Accordingly,the bending process of the metal plate 140A, which will later bedescribed, may be easily performed, and occurrence of a spring-backphenomenon may be minimized or reduced, particularly after the bendingprocess.

In an embodiment, the metal plate 140A may have a substantially planartop surface and a substantially planar bottom surface. In an embodiment,the top surface and/or the bottom surface of the metal plate 140A may besubjected to insulation treatment. In some examples, a thin insulationfilm may be located on the top surface of metal plate 140A by forming athin oxide layer (e.g., an anodizing layer) through a metal oxidationprocess or coating or laminating an insulation resin (e.g., polyimide,polypropylene, or polyethylene). In some examples, the top surface ofthe metal plate 140A may correspond to the interior surface of the can140, and the bottom surface of the metal plate 140A may correspond tothe exterior surface of the can 140. These features of the metal plate140A may be commonly applied to all of the metal plates disclosed in thefollowing embodiments.

FIG. 3B shows the metal plate 140A at a later stage of manufacture.

In the example shown in FIG. 3B, the substantially planar metal plate140A having a uniform thickness may be provided using a blanking processand/or a notching process. In some examples, the metal plate 140A mayinclude a substantially rectangular bottom portion 141 having long sidesand short sides, long side portions 142 and 143 (to later be bent fromthe bottom portion) horizontally extended from the respective long sidesof the bottom portion 141, and short side portions 144 and 145 (to laterbe bent from the bottom portion and the long side portions) horizontallyextended from the bottom portion 141 and the respective long sideportions 142 and 143.

In some examples, one of the short side portions 144 may include a firstshort side portion 144 a extended from the short side of the bottomportion 141 in a substantially triangular shape, a second short sideportion 144 b horizontally extended from an end of the long side portion142, and a third short side portion 144 c horizontally extended from anend of the long side portion 143. In an embodiment, the second shortside portion 144 b may include an inclined periphery located on a regionfacing the first short side portion 144 a, and the third short sideportion 144 c may also include an inclined periphery located on a regionfacing the first short side portion 144 a. In other words, the secondand third short side portions 144 b and 144 c may be configured to matchor correspond with the first short side portion 144 a. In an embodiment,the width of each of the long side portions 142 and 143 may besubstantially equal to that of each of the long sides of the bottomportion 141. In an embodiment, the width of the first short side portion144 a may be substantially equal to that of each of the short sides ofthe bottom portion 141. In addition, the overall width of the second andthird short side portions 144 b and 144 c may be substantially equal tothe width of each of the short sides of the bottom portion 141. Inaddition, the length of each of the long side portions 142 and 143 maybe substantially equal to that of each of the short side portions 144and 145. In FIG. 3B, dashed lines indicate bending lines in a subsequentprocess to be described later.

FIGS. 4A to 4D are partially enlarged plan views illustrating an examplemethod for manufacturing an example secondary battery. For clarity andbrevity, FIG. 4A shows a first short side portion 144 a extended from abottom portion 141, and second and third short side portions 144 b and144 c extended from the long side portions 142 and 143, respectively.

As shown in FIG. 4B, in a region “4 b,” in some examples, at least oneor more curvatures 1440A may be provided between the first short sideportion 144 a and the second short side portion 144 b, for example, aregion where the first short side portion 144 a and the second shortside portion 144 b meet, a connecting region where the first short sideportion 144 a and the second short side portion 144 b are connected toeach other, a vertex between the first short side portion 144 a and thesecond short side portion 144 b, a corner between the first short sideportion 144 a and the second short side portion 144 b, or a corner jointregion between the first short side portion 144 a and the second shortside portion 144 b.

In addition, as shown in FIG. 4C, in a region “4 c,” in some examples,at least one or more curvatures 1440B may be provided between the firstshort side portion 144 a and the third short side portion 144 c, forexample, a region where the first short side portion 144 a and the thirdshort side portion 144 c meet, a connecting region where the first shortside portion 144 a and the third short side portion 144 c are connectedto each other, a vertex between the first short side portion 144 a andthe third short side portion 144 c, a corner between the first shortside portion 144 a and the third short side portion 144 c, or a cornerjoint region between the first short side portion 144 a and the thirdshort side portion 144 c.

In some examples, the curvatures 1440A may include a first curvature1441 located in the first short side portion 144 a and a secondcurvature 1442 located in the second short side portion 144 b.

In addition, in some examples, the curvatures 1440B may include a firstcurvature 1441 located in the first short side portion 144 a, and athird curvature 1443 located in the third short side portion 144 c.

In addition, in some examples, the first curvature 1441 and the secondcurvature 1442 may be in an asymmetric configuration with respect to abending line between the bottom portion 141 and the long side portion142. In addition, in some examples, the first curvature 1441 and thethird curvature 1443 may be in an asymmetric configuration with respectto a bending line between the bottom portion 141 and the long sideportion 143.

As shown in FIG. 4B, in some examples, the first curvature 1441 may belarger (e.g., have a larger area) than the second curvature 1442. Inaddition, as shown in FIG. 4C, in some examples, the first curvature1441 may be larger (e.g., have a larger area) than the third curvature1443, or vice versa.

In some examples, the first, second, and third curvatures 1441, 1442,and 1443 may be circular or elliptical. In addition, in some examples,if the first, second, and third curvatures 1441, 1442, and 1443 arecircular, the first curvature 1441 may have a larger curvature radiusthan the second curvature 1442, as shown in FIG. 4B. In addition, asshown in FIG. 4C, the first curvature 1441 may have a larger curvatureradius than the third curvature 1443, or vice versa.

In some examples, the curvature radius of the first curvature 1441 maybe approximately 5 to 11 times, and, in an embodiment, 7 to 9 times,that of the second curvature 1442. Within this numerical range, adesirably shaped curved portion 1550A (see FIG. 6C) may be provided at aregion where the bottom portion 141, the long side portion 142, and theshort side portions including the first short side portion 144 a havingthe first curvature 1441, and the second short side portion 144 b havingthe second curvature 1442, meet. In some examples, the curvature radiusof the first curvature 1441 may be approximately 5 to 11 times, and, inan embodiment, 7 to 9 times, larger than that of the third curvature1443. Within this numerical range, a desirably shaped curved portion1550B (see FIG. 6C) may be provided at a region where the bottom portion141, the long side portion 143, and the short side portions includingthe first short side portion 144 a having the first curvature 1441, andthe third short side portion 144 c having the third curvature 1443,meet.

As described above and with reference to FIG. 4D, in an embodiment, acurvature radius R1 of the first curvature 1441 may be larger than acurvature radius R2 of the second curvature 1442, and the firstcurvature 1441 and the second curvature 1442 may be consecutivelyconnected to each other. In an embodiment, the curvature radius of thefirst curvature 1441 may be larger than that of the third curvature1443, and the first curvature 1441 and the third curvature 1443 may beconsecutively connected to each other.

FIGS. 5A and 5B are partially enlarged plan views illustrating anexample method for manufacturing an example secondary battery. As shownin FIGS. 5A and 5B, in some examples, the second curvature 1442 may belarger (e.g., have a larger area) than the first curvature 1441. Inaddition, as shown in FIG. 5B, in some examples, the third curvature1443 may be larger (e.g., have a larger area) than the first curvature1441.

In some examples, the first, second, and third curvatures 1441, 1442,and 1443 may be circular or elliptical, and the second curvature 1442may have a larger curvature radius than the first curvature 1441. Inaddition, in some examples, the third curvature 1443 may have a largercurvature radius than the first curvature 1441. In some examples, thefirst, second, and third curvatures 1441, 1442, and 1443 are provided byblanking and/or notching the metal plate 140A. Therefore, thicknesses ofthe first, second, and third curvatures 1441, 1442, and 1443 may beequal to or similar to those of the bottom portion 141, the first shortside portion 144 a, the second short side portion 144 b, and the thirdshort side portion 144 c.

FIGS. 6A to 6C are perspective views illustrating an example method formanufacturing an example secondary battery. FIGS. 6A and 6B show themetal plate 140A at a later stage of manufacture. In the example shownin FIGS. 6A and 6B, the metal plate 140A may be bent in a shape (e.g., apredetermined shape). In some examples, the metal plate 140A may be bentin a predetermined shape after it is fixed by a bending machine or apress mold.

In some examples, the long side portions 142 and 143 bent and extendedfrom the respective long sides of the bottom portion 141 in asubstantially perpendicular direction, and the short side portions 144and 145 bent and extended from the bottom portion 141 and the long sideportions 142 and 143 in a substantially perpendicular direction, may beprovided as the result of the bending process. That is, in anembodiment, the long side portions 142 and 143 may be bent approximately90 degrees from the long sides of the bottom portion 141 to be extended,and the short side portions 144 and 145 may be bent approximately 90degrees from the short sides of the bottom portion 141 to be extendedand may be bent approximately 90 degrees from the long side portions 142and 143 to be extended.

Therefore, the first short side portion 144 a, the second short sideportion 144 b, and the third short side portion 144 c may be positionedto face one another and their peripheries may contact one another. In anembodiment, an angle of a vertex of the first short side portion 144 a,facing the second and third short side portions 144 b and 144 c may bein a range from approximately 80 degrees to approximately 100 degrees,and, in an embodiment, 90 degrees.

In some examples, an angle defined between each of two upper peripheriesof the first short side portion 144 a and the short side of the bottomportion 141 may be in a range from approximately 40 degrees toapproximately 50 degrees, and, in an embodiment, 45 degrees, an angledefined between the periphery of the second short side portion 144 bfacing an end of the periphery of the first short side portion 144 a andan end of the long side portion 142 may be in a range from approximately40 degrees to approximately 50 degrees, and, in an embodiment, 45degrees, and an angle defined between the periphery of the third shortside portion 144 c facing another end of the periphery of the firstshort side portion 144 a and an end of the long side portion 143 may bein a range from approximately 40 degrees to approximately 50 degrees,and, in an embodiment, 45 degrees. Accordingly, a vertex at which thebottom portion 141, the end of the long side portion 142, the firstshort side portion 144 a, and the second short side portion 144 b meet,and a vertex at which the bottom portion 141, the end of the long sideportion 143, the first short side portion 144 a, and the third shortside portion 144 c meet, may be bent in a substantially round shape.

In some examples, a pair of asymmetrical curvatures 1440A (1441 and1442) are provided at a region or vertex where the first short sideportion 144 a and the second short side portion 144 b meet, and a pairof asymmetrical curvatures 1440B (1441 and 1443) are provided at aregion or vertex where the first short side portion 144 a and the thirdshort side portion 144 c meet, thereby providing a curved portion 1550A(see FIG. 6C) at a region where the bottom portion 141, the long sideportion 142, and the short side portions including the first short sideportion 144 a having the first curvature 1441 and the second short sideportion 144 b having the second curvature 1442, meet, and a curvedportion 1550B (see FIG. 6C) at a region where the bottom portion 141,the long side portion 143, and the short side portions including thefirst short side portion 144 a having the first curvature 1441 and thethird short side portion 144 c having the third curvature 1443 meet.FIG. 6B shows an example in which the short side portions 144 and 145are bent from the long side portions 142 and 143, respectively. That is,FIG. 6B shows an example in which the long side portions 142 and 143have yet to be bent from the bottom portion 141.

FIG. 6C shows the can 140 at a later stage of manufacture. In theexample shown in FIG. 6C, a bending process and a welding process may beperformed.

Similarly as above, in some examples, when the long side portion 142,the first short side portion 144 a, and the second short side portion144 b are bent with respect to the bottom portion 141, the curvatures1440A, i.e., the first curvature 1441 and the second curvature 1442, arepositioned to overlap with each other or to be piled up one on another,thereby providing the symmetrical curved portion 1550A at a corner wherethe bottom portion 141, the long side portion 142, the first short sideportion 144 a, and the second short side portion 144 b meet.

In addition, in some examples, when the long side portion 143, the firstshort side portion 144 a, and the third short side portion 144 c arebent with respect to the bottom portion 141, the curvatures 1440B, i.e.,the first curvature 1441 and the third curvature 1443, are positioned tooverlap with each other or to be piled up one on another, therebyproviding the symmetrical curved portion 1550B at a corner where thebottom portion 141, the long side portion 143, the first short sideportion 144 a, and the third short side portion 144 c meet.

In addition, in some examples, the welding portions 146 may be providedin the short side portions 144 and 145. In some examples, the weldingportions 146 may include a first welding portion 146 a, a second weldingportion 146 b, and a third welding portion 146 c. The first weldingportion 146 a may extend from the curved portion 1550A provided at acorner where the bottom portion 141, the long side portion 142, thefirst short side portion 144 a, and the second short side portion 144 bmeet, and along a boundary region between the first short side portion144 a and the second short side portion 144 b. The second weldingportion 146 b may extend from the curved portion 1550B provided at acorner where the bottom portion 141, the long side portion 143, thefirst short side portion 144 a, and the second short side portion 144 bmeet, and along a boundary region between the first short side portion144 a and the third short side portion 144 c. The third welding portion146 c may be located at a boundary region between the second short sideportion 144 b and the third short side portion 144 c.

In other words, the first welding portion 146 a may be at an acute anglewith respect to a short side of the bottom portion 141 in the curvedportion 1550A where the bottom portion 141, the end of the long sideportion 142, the first short side portion 144 a, and the second shortside portion 144 b meet, and the second welding portion 146 b may be atan acute angle with respect to the short side of the bottom portion 141in the curved portion 15506 where the bottom portion 141, the end of thelong side portion 143, the first short side portion 144 a, and the thirdshort side portion 144 c meet. In addition, the third welding portion146 c may extend from a bottom end of the second and third short sideportions 144 b and 144 c to a top end (i.e., an opening 147) of thesecond and third short side portions 144 b and 144 c.

In some examples, the first and second welding portions 146 a and 146 bmay be consecutively formed, and the third welding portion 146 c maythen be formed, or vice versa. In an embodiment, the welding process maybe performed on the first welding portion 146 a, the third weldingportion 146 c, and the second welding portion 146 b in that order, orthe welding order may be reversed. In addition, the welding processperformed on the third welding portion 146 c may be started from thebottom end and may be terminated at the top end, or vice versa. In someexamples, the first, second, and third welding portions 146 a, 146 b,and 146 c may include a butt joint structure, a lap joint structure, anoverlay joint structure, or an edge joint structure. In some examples,the welding portions 146 may be in a substantially inverted Y-shaped (“

”) configuration. The welding portions 146 may be provided to have asolid-line shape. Therefore, the first short side portion 144 a may besecurely fixed to the second and third short side portions 144 b and 144c due to the first and second welding portions 146 a and 146 b, and thesecond and third short side portions 144 b and 144 c may be securelyfixed to each other by the third welding portion 146 c.

In an embodiment, the first and second welding portions 146 a and 146 bconnected to each other may be shaped as straight lines having at leastone vertex, and the third welding portion 146 c may be shaped as astraight line extending from the vertex, where the first and secondwelding portions 146 a and 146 b meet, to the opening 147. In anembodiment, a vertex angle defined between the first welding portion 146a and the second welding portion 146 b may be in a range fromapproximately 80 degrees to approximately 100 degrees, and, in anembodiment, 90 degrees. In addition, an angle in a range fromapproximately 40 degrees to approximately 50 degrees, and, in anembodiment, 45 degrees, may be defined between the first welding portion146 a and the short side of the bottom portion 141, and an angle in arange from approximately 40 degrees to approximately 50 degrees, and, inan embodiment, 45 degrees, may also be defined between the secondwelding portion 146 b and the short side of the bottom portion 141.

As described above, one or more embodiments of the present inventionprovide the can 140 configured such that the first short side portion144 a is bent and extended from the bottom portion 141, and asymmetricalcurvatures 1440A and 1440B are provided at the vertex (corner) betweenthe first short side portion 144 a and the second short side portion 144b and at the vertex (corner) between the first short side portion 144 aand the third short side portion 144 c, thereby providing symmetricalcurved portions 1550A and 15506, which are naturally desirable, atregions where three or four sides meet, respectively. In addition, thefirst, second, and third welding portions 146 a, 146 b, and 146 c areprovided from the curved portions 1550A and 15506 along interfaces(e.g., cutting lines) between each of the first, second, and third shortside portions 144 a, 144 b, and 144 c to be connected to one another todefine a single short side portion 144, thereby providing the can 140having increased bending and welding workability and improved sealingefficiency to prevent or substantially prevent leakage of electrolyte.

Here, as the result of the bending process, curved portions may also beprovided between the bottom portion 141 and the first short side portion144 a, between the bottom portion 141 and each of the long side portions142 and 143, between the long side portion 142 and the second short sideportion 144 b, and between the long side portion 143 and the third shortside portion 144 c.

In some examples, as described above, the curved portion 1550A having around shape may be provided at the corner where the bottom portion 141,the long side portion 142, the first short side portion 144 a, and thesecond short side portion 144 b meet by the asymmetrical curvatures1440A. In addition, as described above, the curved portion 15506 havinga round shape may be provided at the corner where the bottom portion141, the long side portion 143, the first short side portion 144 a andthe third short side portion 144 c meet by the asymmetrical curvatures1440B. In some examples, the curvature radii of the curved portions1550A and 15506 located at regions where three or four sides meet may besmaller than those of the curved portions located at regions where thetwo sides meet, thereby providing the can 140 having a generally stableshape.

In some examples, prior to formation of the welding portions 146, atemporary welding portion may first be provided at a boundary regionbetween the first short side portion 144 a and the second short sideportion 144 b, a boundary region between the first short side portion144 a and the third short side portion 144 c, and/or a boundary regionbetween the second short side portion 144 b and the third short sideportion 144 c. The temporary welding portion may include multipletemporary welding portions spaced apart from one another. In someexamples, the temporary welding portions may be provided to havesubstantially dotted-line shapes. The temporary welding portions mayprevent or substantially prevent a spring-back phenomenon from occurringto the long side portions 142 and 143, the short side portions 144 and145, and the bottom portion 141. In addition, the temporary weldingportions may securely fix the long side portions 142 and 143 and theshort side portions 144 and 145 to each other. Accordingly, the mainwelding portions 146 (i.e., the welding portions 146) may be easilyprovided. In an embodiment, the temporary welding portions may beprovided by ultrasonic welding or resistance welding, as well as laserwelding.

FIGS. 7A and 7B are partially enlarged plan views illustrating a methodfor manufacturing a secondary battery according to an exampleembodiment.

As shown in FIG. 7A, in some examples, a curvature 1440C may be providedsubstantially at the center of a region where a first short side portion144 a and a second short side portion 144 b (or a third short sideportion) meet. In some examples, the curvature 1440C may be providedsubstantially at the center of the region where the first short sideportion 144 a and the second short side portion 144 b (or the thirdshort side portion) meet, in a substantially symmetrically round shape,but the shape of the curvature 1440C is not limited thereto. Rather, thecurvature 1440C may have any of the shapes of the above-describedcurvatures.

As shown in FIG. 7B, in some examples, a curvature 1440D may beconnected longer (or more widely) to the second short side portion 144 b(or the third short side portion) than to the first short side portion144 a. In some other examples, the curvature 1440D may be connectedlonger (or more widely) to the first short side portion 144 a than tothe second short side portion 144 b (or the third short side portion).Accordingly, in some examples, the curvature 1440D may have anasymmetric configuration around a region where the first short sideportion 144 a and the second short side portion 144 b meet (e.g., avertex or a corner). Similarly as above, the curvature 1440D may beprovided in a substantially round shape, but the shape of the curvature1440D is not limited thereto. Rather, the curvature 1440D may have anyof the shapes of the above-described curvatures.

As described above, when a metal plate is blanked and/or notched, thecurvatures 1440A, 14408, 1440C, and 1440D may be integrally formed atthe boundary region between the first short side portion 144 a and thesecond short side portion 144 b or at the boundary region between thefirst short side portion 144 a and the third short side portion 144 c.

In addition, in some examples, the long side portions 142 and 143 andthe first short side portion 144 a are bent from the bottom portion 141,and the second and third short side portions 144 b and 144 c are bentfrom the long side portions 142 and 143, as described above, thecurvatures 1440A, 1440B, 1440C, and 1440D, to then be inserted orconnected to the corner regions of three or four sides, where these sideportions meet (for example, a region where the first short side portion144 a and the second short side portion 144 b meet, and a region wherethe first short side portion 144 a and the third short side portion 144c meet).

As described above, since the curvature(s) are located at the regionswhere the first short side portion bent from the bottom portion and thesecond and third short side portions bent from the long side portionsmeet, desirably shaped curved portions in a symmetric configuration maybe provided at the regions (corners) where the bottom portion, the longside portions, and the first, second, and third short side portions meetby the curvatures when the first short side portion and the second andthird short side portions are bent. In addition, since the desirablyshaped curved portions in a symmetric configuration are provided by thecurvature(s), and distances between boundary regions of the curvedportions and the first, second, and third short side portions arereduced, welding can be easily performed, thereby preventing orsubstantially preventing pinholes from being generated at the boundaryregions. In addition, when multiple batteries are assembled or stackedto manufacture a battery module or pack at a later stage, thesymmetrical curved portions may not interfere with other batteries,thereby preventing or substantially preventing insulation breakdownsfrom occurring among the batteries. However, if the curved portions wereasymmetrically configured, insulation layers of other neighboringbatteries may be damaged by the asymmetrical curved portions, resultingin insulation breakdowns among the neighboring batteries.

While the secondary battery of the present invention has beenparticularly shown and described with reference to some exampleembodiments thereof, it will be understood by those of ordinary skill inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asset forth by the following claims.

What is claimed is:
 1. A secondary battery comprising: an electrodeassembly; a case accommodating the electrode assembly; and a capassembly coupled to the case to seal the case, wherein the casecomprises a bottom portion, long side portions bent and extended fromthe bottom portion, a first short side portion bent and extended fromthe bottom portion, and second short side portions bent and extendedfrom the long side portions, the first short side portion and the secondshort side portions connected to each other to define a short sideportion, and curvatures located between the first short side portion andthe second short side portions.
 2. The secondary battery of claim 1,wherein the curvatures are located at regions where the first short sideportion and the second short side portions meet.
 3. The secondarybattery of claim 1, wherein the curvatures comprise: a first curvaturelocated in the first short side portion, and a second curvature locatedin each of the second short side portions.
 4. The secondary battery ofclaim 3, wherein the first curvature and the second curvature overlapwith each other.
 5. The secondary battery of claim 3, wherein the firstcurvature and the second curvature are in an asymmetric configuration.6. The secondary battery of claim 3, wherein the first curvature islarger than the second curvature.
 7. The secondary battery of claim 3,wherein the second curvature is larger than the first curvature.
 8. Thesecondary battery of claim 3, wherein the first curvature has a largercurvature radius than the second curvature.
 9. The secondary battery ofclaim 3, wherein the second curvature has a larger curvature radius thanthe first curvature.
 10. The secondary battery of claim 3, furthercomprising curved portions located at regions where the bottom portion,the long side portions, and the short side portion comprising the firstshort side portion having the first curvature, and the second short sideportion having the second curvature, meet.
 11. The secondary battery ofclaim 10, wherein the short side portion further comprises weldingportions, and the welding portions comprise a first welding portionlocated between each of the curved portions and each of the first shortside portion and the second short side portions, and a second weldingportion located between the second short side portions.
 12. Thesecondary battery of claim 1, wherein the curvatures are located atcenters of regions where the first short side portion and the secondshort side portions meet.
 13. The secondary battery of claim 1, whereinthe curvatures are connected longer to the first short side portion thanto the second short side portions, or the curvatures are connectedlonger to the second short side portions than to the first short sideportion.
 14. The secondary battery of claim 1, wherein the first shortside portion extends from both end portions of the bottom portion, thesecond short side portions extend from both ends of the long sideportions, and the short side portion is defined on both sides of thebottom portion and the long side portions.